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United States Patent |
5,741,742
|
Kamide
|
April 21, 1998
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Formation of aluminum-alloy pattern
Abstract
A method of forming an aluminum-alloy pattern at room temperature, which is
capable of eliminating the generation of after-corrosion and enhancing the
anisotropic processing. In a first step, an etching mask made of a silicon
nitride based film is formed on an aluminum-alloy film formed on a barrier
metal layer which is formed on a substrate. In a second step, the
aluminum-alloy film is dry-etched at room temperature, to form a pattern
of the aluminum-alloy film. The etching selection ratio of the
aluminum-alloy film to the etching mask is thus improved, and further a
sidewall protective film made of aluminum nitride is formed on the etching
sidewall, thereby sufficiently performing the anisotropic processing for
the aluminum-alloy pattern. In subsequent steps, the barrier metal layer
may also be etched and removed at room temperature, and a further sidewall
protective film made of aluminum oxide is formed on the etching sidewall
as a result of oxygen plasma processing. Any remaining barrier metal layer
may be perfectly removed as a final step as a result of over-etching.
Inventors:
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Kamide; Yukihiro (Kanagawa, JP)
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Assignee:
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Sony Corporation (Tokyo, JP)
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Appl. No.:
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695526 |
Filed:
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August 12, 1996 |
Foreign Application Priority Data
Current U.S. Class: |
438/653; 257/E21.311; 438/688; 438/696; 438/717 |
Intern'l Class: |
H01L 021/283; H01L 021/31 |
Field of Search: |
437/190,194,199,197,228
156/643.1,653.1,656.1
438/653,688,695,696,706,717,963
|
References Cited
U.S. Patent Documents
4828649 | May., 1989 | Davis et al. | 156/643.
|
4915779 | Apr., 1990 | Srodes et al. | 156/643.
|
5024722 | Jun., 1991 | Cathey, Jr. | 156/643.
|
5217570 | Jun., 1993 | Kadomura | 156/665.
|
5369053 | Nov., 1994 | Fang | 437/194.
|
Foreign Patent Documents |
62-238649 | Oct., 1987 | JP | 437/194.
|
1-80044 | Mar., 1989 | JP | 437/194.
|
4-330724 | Nov., 1992 | JP | 437/199.
|
5-109673 | Apr., 1993 | JP | 437/194.
|
Other References
Kamide et al, "HBr Added High Selective Etch Process of Al Alloy
Multi-Layers", Proceedings of the 4th Symposium on Semiconductors and
Integrated Circuits Technology, Dec. 19-20, 1991, pp. 121-126.
Aoki et al, "After-Corrosion Suppression Using Low-Temperature Al-Si-Cu
Etching", Proceedings of Symposium on Dry Process, Nov. 1-2, 1990 pp.
141-145.
|
Primary Examiner: Quach; T. N.
Attorney, Agent or Firm: Kananen; Ronald P.
Parent Case Text
This application is a continuation of application Ser. No. 08/300,222 filed
Sep. 6, 1994, abandoned.
Claims
What is claimed is:
1. A method of manufacturing an integrated semiconductor device comprising
the steps of:
forming a barrier metal layer over a substrate;
forming a conductive layer of aluminum-alloy over said barrier metal layer;
providing a patterned mask layer comprising a silicon nitride based film on
the conductive layer, the mask layer having a resistance against an
etching gas used for etching the conductive layer and a function of
supplying a component forming a film for protecting a sidewall of the
conductive layer;
patterning the conductive layer by dry-etching by using the patterned mask
layer at or about room temperature wherein said mask layer deposits a
protection film on the sidewall of the conductive layer;
patterning the barrier metal layer by dry-etching;
oxygen plasma processing for forming aluminum oxide on the side wall of the
conductive layer; and
over-etching for perfectly removing the remaining part of the barrier metal
layer on the substrate.
2. A method of manufacturing an integrated semiconductor device according
to claim 1, wherein a reflection preventive layer film is provided between
the conductive layer and the patterned mask layer.
3. A method of manufacturing an integrated semiconductor device
comprising-the steps of:
forming a barrier metal layer over a substrate;
forming a conductive layer of aluminum-alloy over said barrier metal layer;
providing a double-layered mask on the conductive layer, the double-layered
mask comprising a lower mask having a resistance against an etching gas
used for etching the conductive layer and an upper layer comprising a
silicon nitride based film for supplying a component forming a film for
protecting a sidewall of the conductive layer upon etching the conductive
layer;
patterning the conductive layer by dry-etching by using the double-layered
mask at or about room temperature wherein said upper layer deposits a
protection film on the sidewall of the conductive layer;
oxygen plasma processing for removing said upper mask layer and forming
aluminum oxide on the side wall of the conductive layer;
patterning the barrier metal layer by dry-etching; and
over-etching for perfectly removing the remaining part of the barrier metal
layer on the substrate.
4. A method of manufacturing an integrated semiconductor device according
to claim 3, wherein the lower layer mask comprises at least one substance
selected from the group consisting of a silicon nitride based film and a
silicon oxide based film.
5. A method of manufacturing an integrated semiconductor device according
to claim 3, wherein a reflection preventive film is provided between the
conductive layer and the patterned mask layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing an integrated
semiconductor device, and particularly to a method of forming a conductive
layer of aluminum-alloy in the integrated semiconductor device.
2. Description of Related Art
Aluminum-alloys are variously used as materials of metallization and
electrodes formed on substrates in semiconductor integrated circuits. The
metallization and electrodes using these aluminum-alloy are generally
formed by dry-etching with a mixture gas containing a chlorine based gas
using photoresist as an etching mask. In this dry-etching, the decomposed
component of the photoresist by dry-etching is stuck on etching sidewall
for forming a sidewall protective film, thus achieving the anisotropic
shape of the formed aluminum-alloy pattern.
In recent years, aluminum-alloy patterns with fine structures have been
required, along with strong demands in the field of semiconductor
integrated circuits toward the high integration and the high function.
A thin photoresist film must be used for precisely forming an
aluminum-alloy pattern with fine line-widths in terms of the
photosensitivity of the photoresist used for the etching mask.
On the other hand, the aluminum-alloy pattern with fine line-widths must be
somewhat thick in the film thickness for keeping the reliability against
electromigration.
Accordingly, to form the above aluminum-alloy pattern on the semiconductor
integrated circuit with a fine structure, it is required to etch the
aluminum-alloy film while suppressing the consumption of the thinned
photoresist film by improving the etching selection ratio between the
photoresist and the aluminum-alloy.
There have been proposed a process of performing the above etching by
suppressing the incident energy of etching ions for improving the
resistance of a photoresist film against the etching ions, and a process
of performing the above etching while forming a protective film on the
peripheral wall of an photoresist film.
Moreover, there has been proposed a process using an inorganic material
such as silicon oxide as an etching mask. In this process, the resistance
of the etching mask is improved; however, a sidewall protective film is
not formed on an etching sidewall by the usual etching method performed at
room temperature. As a result, the aluminum-alloy pattern cannot be formed
in an anisotropic shape.
However, it is reported that an anisotropic shape can be obtained by
performing the dry-etching by cooling the substrate temperature at a lower
temperature less than 0.degree. C.
An anisotropic shape of an aluminum-alloy pattern can be also obtained by
the dry-etching using an etching gas which is added with a gas for forming
a sidewall protective film on an etching sidewall made of an
aluminum-alloy film, for example nitrogen gas.
However, the above-described processes have the following disadvantages.
Namely, in the case of forming an aluminum-alloy pattern on a substrate, a
barrier metal layer made of, for example titanium oxy-nitride is formed
between the substrate and the aluminum-alloy pattern, and the barrier
layer is also dry-etched together with the above aluminum-alloy pattern.
In this dry-etching, the etching rate of titanium oxy-nitride is dependent
on the incident energy of etching ions contained in an etching gas.
Accordingly, in the prior art process of performing the etching while
suppressing the incident energy of etching ions, the total consumption of
the photoresist in the etching for the aluminum-alloy film and the barrier
metal layer cannot be suppressed, and thereby the etching mask is consumed
before the etching is sufficiently performed.
In the prior art process of forming a protective film on the peripheral
wall of a photoresist film, the protective film is difficult to be
separated in the subsequent process, which causes a fear in generating
after-corrosion due to chlorine as the component of the etching gas
contained in the protective film.
In the process using an inorganic material as an etching mask wherein the
etching is performed by cooling a substrate temperature at a lower
temperature less than 0.degree. C., there are disadvantages that the
equipment cost is increased; and various gas molecules in the etching
atmosphere are stuck on a sample because of the etching performed at a low
temperature, causing the generation of after-corrosion.
Moreover, in the case of the dry-etching using an etching gas added with
nitrogen gas, a material forming a sidewall protective film is scattered
in a chamber, which causes the contamination in the interior of the
chamber.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of forming an
aluminum-alloy pattern at room temperature, which is capable of
eliminating the generation of after-corrosion and enhancing the
anisotropic processing.
To achieve the above object, according to a first invention, there is
provided a method of forming an aluminum-alloy pattern, including the
steps of: forming an etching mask made of silicon nitride based film on an
aluminum-alloy film formed on a substrate, and dry-etching the
aluminum-alloy film at room temperature for forming a pattern of the
aluminum-alloy film.
Moreover, according to a second invention, there is provided a method of
forming an aluminum-alloy pattern, including the steps of: forming, on an
aluminum-alloy film formed on a substrate, an etching mask having a
layered structure of a lower layer mask having a resistance against an
etching gas used for dry-etching the aluminum-alloy film and an upper
layer mask for supplying a component forming a sidewall protective film on
an etching sidewall upon dry-etching the aluminum alloy film, and
dry-etching the aluminum-alloy film at room temperature for forming a
pattern of the aluminum-alloy film.
In the above second invention, the lower layer comprises a silicon nitride
based film or a silicon oxide based film and the upper layer comprises a
resist film or silicon nitride based film.
The dry-etching method in the present invention is made to etch a
conductive pattern of aluminum-alloy by the multiplier effect of a neutral
active seed and reactive gas ions using reactive gas plasma.
The silicon nitride based film in the present invention may include a
silicon nitride film, a silicon oxy-nitride film and a plasma silicon
nitride (P--SiN) film; and the silicon oxide film in the present invention
may include a silicon dioxide film and a plasma TEOS oxide film.
In the method of forming an aluminum-alloy pattern according to the first
invention, the dry-etching for an aluminum-alloy film is performed using a
silicon nitride based film as an etching mask. The silicon nitride film
has a resistance for an etching gas used for dry-etching the
aluminum-alloy film. Accordingly, the etching selection ratio of the
aluminum-alloy film is improved, and the etching for forming the
aluminum-alloy film is sufficiently performed using the silicon nitride
film as an etching mask. Moreover, the silicon nitride based film releases
nitrogen upon dry-etching the aluminum-alloy film. The nitrogen thus
released forms a sidewall protective film made of aluminum nitride on the
etching sidewall. The aluminum-alloy pattern is thus formed in an
anisotropic shape by this etching. Moreover, the above dry etching is
performed at room temperature, so that gas molecules in the etching
atmosphere are not absorbed by the substance to be etched.
Next, in the method of forming an aluminum-alloy pattern according to the
second invention, the dry-etching for an aluminum-alloy pattern is
performed using an etching mask having a layered structure of an upper
layer mask and a lower layer mask. First, the dry-etching for the
aluminum-alloy film is performed using the upper layer mask for supplying
a component forming a sidewall protective film on an etching sidewall. As
a result, the aluminum-alloy pattern formed by this etching becomes an
anisotropic shape. After that, the dry-etching for the aluminum-alloy film
is performed using the lower layer mask having a resistance against
etching ions used for the dry-etching of the aluminum-alloy film. As a
result, it becomes possible to sufficiently dry-etch the aluminum-alloy
film by improvement in the etching selection ratio of the aluminum-alloy
film. Moreover, since the dry-etching is performed at room temperature,
gas molecules in the etching atmosphere are not absorbed by the substance
to be etched.
In the case using a resist film as the upper layer, the decomposed material
of the resist film is formed as the above sidewall protective film. In the
case using a silicon nitride based film as the upper layer mask, an
aluminum nitride film is formed as the sidewall protective film. Moreover,
in the case using a silicon nitride based film or silicon oxide based
film, there can be obtained the etching mask having a resistance against
an etching gas used for dry-etching the aluminum-alloy film.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1A to 1C are typical sectional views for illustrating a first
embodiment;
FIGS. 2A to 2B are typical sectional views for illustrating the first
embodiment;
FIGS. 3A to 3B are typical sectional views for illustrating a second
embodiment; and
FIGS. 4A to 4C are typical sectional views for illustrating the second
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
A first embodiment of the present invention will be described with
reference to FIGS. 1A to 1C and FIGS. 2A to 2B.
First, as shown in FIG. 1A, a barrier metal layer 15 having a layered
structure of a titanium film 12, a titanium oxy-nitride film 13 and a
titanium film 14 was formed by sputtering on the upper surface, made of an
oxide film, of a substrate 11.
An aluminum-alloy film 16 containing, for example 1% of silicon was formed
on the upper surface of the barrier metal layer 15.
First, as a first step, a TiON film was formed as a reflection preventive
film 17 on the upper surface of the aluminum-alloy film 16. A plasma
silicon nitride (P--SiN) 18 having a thickness of 300 nm was formed on the
upper surface of the reflection preventive film 17 by plasma CVD.
After that, a resist film (not shown) was formed on the upper surface of
the P--SiN film 18 by the resist coating of the usual photolithography
process. The resist film was subjected to sensitization and development,
thus forming a resist mask (not shown) in which the resist film is
patterned to a metallization pattern.
Subsequently, the portion of the P--SiN film 18 shown by the two-dotted
line was removed, for example by reactive ion etching using the above
photoresist mask as an etching mask, to form an etching mask 19 patterned
to the metallization pattern.
As one example of the etching condition, a mixture gas of CHF.sub.3 and
O.sub.2 was used as the etching gas, and the flow rates of the gases were
set at CHF.sub.3 /O.sub.2 =75/25 sccm. The pressure in the etching
atmosphere was set at 4 Pa, and the RF power was set at 1000 W. The
etching time was set at 10 min.
After that, the above resist mask was removed, for example by ashing using
oxygen plasma, and the remaining resist mask was removed using fuming
nitric acid.
Next, as shown in FIG. 1B, as a second step, the aluminum-alloy film 16 was
dry-etched at room temperature (20.degree. to 40.degree. C.) in a magnetic
field microwave plasma etching apparatus, to form an aluminum-alloy
pattern 20.
As one example of the etching condition, a mixture gas of BCl.sub.3,
Cl.sub.2 and Ar (argon) was used as the etching gas, and the flow rates of
the gases were set at BCl.sub.3 /Cl.sub.2 /Ar=40/60/50 sccm. The pressure
of the etching atmosphere was set at 1 Pa, the microwave power was 950 W,
and the RF power (2 MHz) was 30 W.
In the above etching, the reflection preventive film 17 is first etched by
etching ions, and then the aluminum-alloy film 16 is etched. At this time,
P--SiN forming the etching mask 19 is decomposed by the etching of the
surface of the etching mask 19, to generate nitrogen (N). The etching
sidewall of the aluminum-alloy film 16 is nitrided by the generated
nitrogen (N) as shown by the arrow in the figure, to form a sidewall
protective film 21 made of aluminum nitride (AlNx). The aluminum-alloy
film 16 is etched in the direction substantially perpendicular to the
substrate 11 by the sidewall protective film 21, so that the formed
aluminum-alloy pattern 20 is formed in an anisotropic shape. Moreover,
since the etching mask 19 has a resistance against the etching ions, in
the dry-etching under the above condition, all of the etching mask 19
having a thickness of 300 nm is not consumed.
After the aluminum-alloy pattern 20 was thus formed, the barrier metal 15
was subsequently etched by the above dry-etching, as shown in FIG. 1C.
As shown in FIG. 2A, aluminum oxide (AlOx) 22 was then formed on the
sidewall of the aluminum-alloy pattern 20 by oxygen plasma processing in
the same chamber as in the above etching.
As one example of the oxygen plasma processing, the flow rate of oxygen gas
was set at 200 sccm, the pressure of the processing atmosphere was 2 Pa,
and the microwave power was 950 W. The processing time was set at 10 sec.
Next, the over-etching for perfectly removing the remaining metal on the
substrate 11 was performed in the following condition. A mixture gas of
BCl.sub.3, Cl.sub.2 and Ar was used as an etching gas, and the flow rates
of the gases were set at BCl.sub.3 /Cl.sub.2 /Ar=40/60/50 sccm. The
pressure of the etching atmosphere was set at 1 Pa, and the microwave
power was set at 950 W. The over-etching time was set at 10 sec.
In this over-etching, the sidewall of the aluminum-alloy pattern 20 is
protected by the aluminum oxide (AlOx) 22 formed on the sidewall of the
aluminum-alloy pattern 20.
After that, as shown in FIG. 2B, on the substrate 11, there was formed an
interlayer insulating film 26 having a layered structure of an etching
mask 19 remaining on the aluminum-alloy pattern 20 formed in the above, a
plasma (P)-TEOS (Tetra Ethyl Ortho Silicate) oxide film 23, an ozone
(O.sub.3)-TEOS oxide film 24 planarized on its surface, and a P-TEOS oxide
film 25.
Next, a second embodiment of the present invention will be described with
reference to FIGS. 3A to 3B and FIGS. 4A to 4C.
First, as shown in FIG. 3A, like the first embodiment, a barrier metal
layer 35 having a layered structure of a titanium film 32, a titanium
oxy-nitride film 33 and a titanium film 34 was formed on a substrate 31.
An aluminum-alloy film 36 containing, for example 1% of silicon was formed
on the upper surface of the barrier metal layer 35.
First, as a first step, like the first embodiment, a TiON film was formed
on the upper surface of the aluminum-alloy film 36 as a reflection
preventive film 37. A P-TEOS oxide film 38 having a thickness of 200 nm
was formed on the upper surface of the reflection preventive film 37 by
plasma CVD, and photoresist was coated on the upper surface of the P-TEOS
film 38, to form a resist film 39.
The resist film 39 was then subjected to sensitization and development, and
the portion of the resist film 39 shown by the two-dotted line was
removed, to form an upper layer mask 40 patterned to a metallization
pattern.
A lower layer mask 41 was then formed by etching the P-TEOS oxide film 38
in a magnetic field microwave plasma etching using the upper layer mask 40
as an etching mask. As one example of the etching condition, a mixture gas
of C.sub.4 F.sub.8 and CH.sub.2 F.sub.2 was used as an etching gas. The
flow rates of the gases were set as C.sub.4 F.sub.8 /CH.sub.2 F.sub.2
=15/10 sccm. The pressure of the etching atmosphere was set at 0.1 Pa, the
microwave power was 1200 W, and the RF power (2 MHz) was 30 W. The
over-etching was performed for 70 sec under this condition.
An etching mask 42 having a layered structure of the lower layer mask 41
and the upper layer mask 40 was thus formed.
Next, as shown in FIG. 3B, as a second step, the aluminum-alloy film 36 was
etched by the magnetic field plasma etching apparatus, to form an
aluminum-alloy pattern 43.
As one example of the etching condition, a mixture gas of BCl.sub.3,
Cl.sub.2 and Ar was used as an etching gas. The flow rates of the gases
were set at BCl.sub.3 /Cl.sub.2 /Ar=20/30/50 sccm. The pressure of the
etching atmosphere was set at 2 Pa, the microwave power was set at 950 W,
and the RF power (2 MHz) was set at 30 W. The just-etching was performed
under this condition.
In the above etching, the reflection preventive film 37 is first dry-etched
by etching ions, and the aluminum-alloy film 36 is then dry-etched. At
this time, by etching of the surface of the upper layer mask 40, the
decomposed material of the photoresist forming the upper layer mask 40 is
generated. This decomposed material is stuck on the etching sidewall of
the aluminum-alloy film 36 as shown by the arrow in the figure, to form a
sidewall protective film 44. The aluminum-alloy film 36 is etched in the
direction substantially perpendicular to the substrate 11 by the sidewall
protective film 44.
After the etching of the aluminum-alloy film 36 was completed, as shown in
FIG. 4A, the residue of the upper layer mask 40 made of photoresist and
the sidewall protective film 44 made of the resist decomposition material
were removed by an asher contained in the etching apparatus, and an
aluminum oxide (Al.sub.2 O.sub.3) 45 was produced on the sidewall of the
aluminum-alloy pattern 43.
As one example of the ashing condition, the flow rate of oxygen gas was set
at 200 sccm, the pressure of the processing atmosphere was 2 MPa, the
microwave power was 1200 W, and the processing temperature was 250.degree.
C. The processing was performed for 120 sec on this condition.
Next, as shown in FIG. 4B, the barrier metal 35 was etched in the etching
chamber of the above etching apparatus.
As one example of the etching condition, a mixture gas of BCl.sub.3,
Cl.sub.2 and Ar was used as an etching gas. The flow rates of the gases
were set at BCl.sub.3 /Cl.sub.2 /Ar=20/30/50 sccm. The pressure of the
etching atmosphere was set at 2 Pa, the microwave power was 950 W, and the
RF power (2 MHz) was 30 W.
In this etching, the sidewall of the aluminum-alloy pattern 43 is protected
by aluminum oxide (AlOx) formed on the sidewall formed on the
aluminum-alloy pattern 43. Moreover, since the lower layer mask 41 made-of
SiO.sub.2 having a resistance against incident etching ions by the etching
covers the surface of the aluminum-alloy pattern 43, it becomes possible
to ensure the anisotropic shape of the aluminum-alloy pattern 43.
After that, as shown in FIG. 4C, like the first embodiment, on the
substrate 31, there was formed an interlayer insulating film 49 having a
layered structure of the lower layer mask 41 remaining on the
aluminum-alloy pattern 43, a P-TEOS oxide film 46, a planarized O.sub.3
-TEOS oxide film 47, and a P-TEOS oxide film 48.
In the second embodiment, the etching mask having the layered structure of
the upper layer mask made of photoresist and the lower layer mask made of
silicon oxide (SiO.sub.2) is formed on the aluminum-alloy film. However,
the etching mask may be formed of a layered structure of an upper layer
mask made of silicon nitride based film such as a silicon nitride (SiN)
film or a silicon oxy-nitride (SiON) film, and a lower mask made of
SiO.sub.2. Moreover, it may be formed of a layered structure of an upper
layer made of photoresist and a lower layer mask made of SiN.
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